1. Field of the Invention
The invention relates to an apparatus and method for forming multiple shapes of curtainwall in general, and in particular, stopless butt-joint curtain walls having thermal breaks therein.
2. Description of the Related Art
Modern buildings often have continuous exterior facing panel areas extending around the building exterior. These panel areas can include panels of glass, metal, plastic, granite and the like of single, multiple or composite construction. The panels can be supported by either direct or indirect attachment. In indirect attachment, a building's supporting structural framework is used to support non-bearing walls. These non-bearing exterior walls with metal gridded substructure are referred to as curtainwalls. The problem of easily and permanently installing curtainwalls or replacing glass, facing panels or infills without: 1) exterior stops at the four sides of glass and other facing panels; 2) a thick front width of members known as the "sight line", which may show beyond the stopless glass; 3) glass secured with structural silicone sealant adhesion; 4) the use of an exterior scaffold for exterior application or access to joints; 5) the use of extra metal and elements for providing extruded covers for inside the member central structural element; 6) extensive field labor; 7) wet caulking weather seal field application; 8) high cost of custom engineered adapters and retainers for installing different facing panels, infill or framed operable windows, with different thickness, or located in a different face plane; 9) the chance for air and water infiltration through extra joints because of the use of additional adapters and retainers; 10) high cost when different curtainwall systems are used in different locations of the same building for changing appearance or depth of curtainwall mullions; and 11) the possibility of failure of an integrated structural thermal break when subjected to tension stress, has persisted in the curtainwall community, and these considerations are advantages of this present invention.
One conventional solution for providing a stopless glazing curtainwall is to provide a structural sealant between glass panels and metal members of supporting frame. U.S. Pat. No. 4,552,790 describes an approach for providing a unit that can be glazed without exterior stops or caps using structural sealant. Glass plates are joined with a spacer to seal the edges of the insulated glass panels. Structural sealant is used on two opposite sides of the spacer to bind the spacer to an adjacent inside surface of the glass plate. Application of the structural sealant is performed from the exterior of the building.
U.S. Pat. No. 4,724,637 describes an approach for interior installation of panels with a system for two sided vertical butt glaze. In this system, a factory glazed and assembled frame is insertable between head and sill liners from the building interior. The head and sill liners are visible from the exterior of the building. The glass panels are bonded to a portion of the frame by structural silicone. The use of structural silicone has the disadvantage of being a relatively expensive material. Further, the application of structural silicone to glass panels requires extensive labor, quality assurance and testing. Also, it is not clear how the glass panels would be replaced.
U.S. Pat. No. 4,912,898 describes an approach for providing a curtainwall having a smooth outer surface which is rail free. A curtainwall which is rail free requires butt joints having sufficient strength to hold the panels in place. This patent describes a butt joint which combines both an adhesive with a bracket to securely hold the panels in place. In this system access from outside the building is needed to install the panels.
U.S. Pat. No. 4,841,700 describes a narrow flush glazed framing system for curtainwalls including thermal breaks. A pair of vertical mullions define the outer boundaries of the framing system. Dual panels of glass are supported between the vertical mullions. A vertical intermediate mullion has a deep glazing channel and a slot for forming a shallow glazing channel. A thermal break is positioned in the deep glazing channel and a thermal break filler assembly fits into the slot to form the shallow glazing channel. The thermal break filler assembly includes a thermal break filler element snap fit between a pair of filler halves to form a three piece filler assembly. The thermal break filler assembly makes it possible to reduce the visible mullion face dimension without reducing the depth of the glazing channels of the mullion.